The level of carbon content can be roughly divided into low carbon steel (carbon content is generally less than 0.25%); Medium carbon steel (carbon content is generally between 0.25-0.60%). But there is not a hard line between them.

Carbon is the main alloying element of iron and steel materials, so iron and steel materials can also be called an iron-carbon alloy. The main role of carbon in steel is:

1. The formation of a solid solution structure improves the strength of steel, such as ferrite, austenite structure, and dissolved carbon elements;

2. The formation of a carbide structure can improve the hardness and wear resistance of steel. Such as cementite, namely Fe3C, is a carbide organization.

Therefore, the carbon in the steel, the higher the carbon content, the strength and hardness of steel is higher, but the plasticity and toughness will also be reduced; Conversely, the lower the carbon content, the higher the plasticity and toughness of steel, its strength and hardness will also be reduced.

Therefore, the level of carbon content determines the use of steel: low carbon steel (carbon < 0.25%), generally used as profiles and stamping materials; Medium carbon steel (< 0.6% carbon content), generally used as machinery parts; High carbon steel (carbon content > 0.7%), generally used as tools, cutters, and molds, etc.

The carbon content of seamless steel tube hasn't how much is the actual requirements, many manufacturers under the condition of the steam pipe manufacturing are not very careful and meticulous, cause a lot of engineering projects above problems happened, also has certain harm on China's progress, so after for steam pipeline of carbon content is what has made the detailed requirements, Under the condition of ensuring the stable incineration of the electric arc, the working voltage of the four electrodes is successively increased by 1 ~ 3V to carry out selection, and the pulse working voltage of the five electrodes is generally within the operating scale of 39 ~ 43V. The welding rate mainly depends on the melting depth and the amount of molten metal material filling in the weld, and the melting depth and the amount of metal material filling in the weld depend on the electric welding current and the welding method and limit. Therefore, the welding rate of five-wire arc welding should be selected according to the thickness of the plate. 1.4.2 Welding Rate Five-wire arc welding is suitable for welding current and welding method of the workpiece of thick-wall pipe opening weld. 20g is the steel widely used for stress parts of the heating furnaces. 

Low carbon steel and medium carbon steel three, in which 45# steel is low carbon steel, less than 45# is high carbon steel, high over 45# is medium carbon steel, seamless stitching seamless steel pipe such as no special requirements, are used 20# seamless stitching seamless steel pipe. 20# seamless stitching seamless steel tube material is 20# steel, the compressive strength is slightly higher than 15#, very little heat treatment, no quenching ductility. Cold type plasticity is high, generally, for bending, injection molding, bending and hammer arch production processing, arc welding and understanding of welding characteristics, gas cutting thin thickness small, strict design or more complex appearance of the product is easy to produce cracks. Aluminum alloy seamless steel tube has a high temperature. 

The whole process of laser cutting will form a lot of heat, but the raw material of the heat transfer coefficient of the stainless steel plate is worse, the heat is gathered in the cutting area and leaves, not easy to heat. Compressive strength of seamless aluminum alloy steel tube. High-pressure seamless steel pipe has good indoor temperature and high temperature comprehensive physical properties, strict quality management, suitable for all kinds of work under the premise of high pressure. High-pressure seamless steel pipe is key for the production of high pressure and above the working pressure gas steam boiler pipeline with high-quality carbon steel, alloy tool steel, and stainless steel wear-resistant seamless steel pipe.